*edited in response to replies*
i noticed a couple of interesting phrasings in some slightly related rules (all movement related, anyway)
abusing the rules as written allows for the exploit.
due to odd phrasing in the 3.5 phb any character can take a 5' movement action (not a 5' step)
in any direction, even diagonally, no matter the amount of penalty for doing so. since not mentioned otherwise, the movement could technically be up.
the relevant quotes:
in the phb, under special movement rules is the following:
Minimum Movement: Despite penalties to movement, you can
take a full-round action to move 5 feet (1 square) in any direction,
even diagonally
also in the phb, from the jump skill:
Action: None. A Jump check is included in your movement, so it
is part of a move action. If you run out of movement mid-jump, your
next action (either on this turn or, if necessary, on your next turn)
must be a move action to complete the jump.
(emphasis mine.)
here are the same rules from the d20srd:
you may use a full-round action to move 5 feet (1 square) in any direction, even diagonally
Action
None. A Jump check is included in your movement, so it is part of a move action. If you run out of movement mid-jump, your next action (either on this turn or, if necessary, on your next turn) must be a move action to complete the jump.
(emphasis mine.)
the srd wording is less supportive of the concept, but one could argue technicality. in effect, if you style your movement upward (or diagonally upward) as a jump, and then use the rule of "moving five feet in any direction no matter the dc", and the rule of "must take a move action if you haven't finished your jump" you could claim to be able to jump across unlikely distances. in slow motion.
this also applies to any movement related action, so one can also apply it to balance checks:
http://www.d20srd.org/srd/skills/balance.htm
and just for laughs, here are some epic level jump dc's:
http://www.d20srd.org/srd/epic/skills.htm#balance
(not to mention any other movement related actions... swim or climb checks anyone?
intended as a fun thought exercise, none of my dm's would allow such a thing, and i would likely be dice'd to death by the rest of the party were i to suggest such a thing.
though you might be able to successfully use this rule exploit on balance checks if you only move 5' per round at low levels. that might be how low level thieves manage second story work.
=D